úterý 23. prosince 2014

Wing Cube Loading

How to estimate in advance the behavior of the model? Usually indicates the need to monitor wing loading. But this works only for comparisons approximately equal sized models.
In the Czech magazine RC Revue 6/2011 was an interesting article dealing with the 3D wing loading. For a long time, I wondered how to use the  wing surface load, when that interpretation depend on the size of the model.

For myself, I came up with a similar indicator (wing loading) / wingspan.
I did not know that there is already a recognized indicator that works.

WL = m / S

WCL = WL / sqrt (S)

where:

m     ... Model Weight  [g] or [oz]
S      ... Wing Area [square dm] or [square ft]
WL   ... Wing Surface Load [g/square dm] or [oz/square ft] 
WCL ... Wing Cube Loading [g/cube dm] or [oz/cube ft]

In the English terminology uses the term "Wing Cube Loading" or "3D wing loading."

The numerical values ​​calculated over imperial and metric units are  approximately the same.

After reading the article, I hastened and calculated volume load some of our models. For comparison, I also included the area load divided by wing span. The biplane was wondering bearing area reduced by a factor 0.87 for the respect due to deterioration of the wing interaction.

We have a range of aircraft from about half a meter to 1.4 meters According to the wing loadings, the flying characteristics could not be reliably assumed. Eg. the VA Dragonfly is quite good and relaxed yet agile aircraft - WL is 23.8, while totally unmanageable for a beginner Mini Bee has WL 20.1.

But the Wing Cube Loading (WCL) works fantastically.

All our easily controllable aircraft (regardless of range) have WCL from 3.3 to approximately 6. The coolest Parastar has WCL 3.3. Somewhat difficult to piloting a tiny Champ with Mark 6.1. The vast quickie with difficult piloting - Mini Bee, especially with the original version of the  wing (WCL = 12,3). With the wing from Multiplex Fox minigleder WCL is 10.8 - actually piloting is a little easier, but still significantly more difficult than Champ.

For comparison I added to the table value for a real aircraft - B52 :).
___________________________________________________________
Model                Weight        Wingspan   Effective  Wing        Wing 
                                                            Wing        Loading    Cube
                                                            Area                        Loading
                           [g]              [mm]         [dm2]      [g/dm2]   [g/dm3]
___________________________________________________________
VA Dragonfly          570              1200        24,00     23,8           4,8
Čemech Parastar    420              1200        25,56       6,4           3,3 
Fenix 80                 216               800        11,00      19,8           6,0
SDM WildHavk       580              1380        27,00      21,5           4,1
VA Pitts S2-CX       828              1005        38,36      21,6           3,5 
Telink Toro 900       500                900        24,95      20,0           4,0
Mini Bee                  65                500          3,04      21,4         12,3 
Mini Bee with wing
from MPX Fox          74                495         3,61       20,5         10,8
HobbyZone Champ    42               517         3,61       11,7           6,1
Real B-52
empty                 83914000        56390       37161     2258         11,7
Real B-52
fully loaded        221353000        56390       37161     5957         30.9

Empirically determined normal value of WCL (applies almost exactly as for the calculation of the metric (dm g) as well as imperial (ft and oz)).
_________________________________________________
type of model                                             WCL
_________________________________________________
Slow Models, Thermal Glider                         <4
Trainers, Parkflyer, 3D                                 5-7
Sports Models, Scale Acrobats                    7-10
Sports Models and Scale Models                10-13
Warplanes, Racing Models                           > 13
Full-Scale                                                  15-20

Explanation

Effective Wing Area
 monoplane: actual area
 biplane:      the actual area * 0.87

Effective Wingspan
monoplane: the actual wingspan
biplane:      (Actual total span of both wings) * square root of (0.87)

Simple Web WCL Calculator: http://www.ef-uk.net/data/wcl.htm

     

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